This application relates to a system for wiring a heating element in an electrical appliance to a thermostat switch in a new manner and a new thermostat switch for supporting the new wiring system.
Residential and light commercial cooking appliances often utilize 240 volt split-phase systems, which are a 3-wire, single-phase, mid-point neutral 240 volt power system that is typically provided for residential and light industrial use in the United States. Such a system has two live hot conductors (terminals), and a neutral conductor (terminal). Each live conductor provides a voltage of about 120VAC with respect to the neutral conductor (which is typically grounded), whereas the hot terminals provides a voltage of about 240VAC with respect to each other. Of course, the actual voltages might vary from utility to utility and place to place, such as between 200VAC and 260VAC (100VAC to 130VAC).
Heating appliances, and in particular electric stoves, will typically utilize the 240VAC split-phase power in order to reduce the current draw on the home wiring system, and thus avoid the use of overly thick conductors. Thus, such appliances must be connected to both hot terminals of the power supply, utilizing the split-phase system. Modern appliances also tend to include 120VAC components as well, such a light fixtures or control systems, and thus such appliances will also be connected to the neutral terminal of the power supply as well. In such a case, only one of the hot terminals, along with the neutral terminal, need be utilized to provide the 120VAC power. Furthermore, the neutral conductor is often utilized for safety reasons as well.
Conventionally, thermostats having connections to both hot terminals of the power supply have been utilized in such heating appliances. Often, an “infinite switch” 10 such as the one shown in a simplified schematic in FIG. 2 is utilized as a thermostat switch in the manner shown in the wiring diagram of FIG. 1, or the additional wiring as shown in FIG. 3 may be used. The connections to the power supply and the heating element, and SW1 and SW2, must all carry the maximum heating element current, and thus must be sized for substantial current loads. However, such wiring is wasteful, complicated, and utilizes much more wire than might otherwise be necessary for some appliances. Furthermore, the infinite switch 10 is more complicated than it needs to be.
Desired is a means of reducing this thermostat complexity, and/or reducing the amount of wasteful and/or complicated wiring.